Long-horizon agents collapse in a way that looks like a phase transition, and researchers named it
AspireAI community · arXiv
Studying agents across controlled puzzles, tool use, embodied environments, multi-hop retrieval and Game of Life, this paper argues that long-horizon LLM agents deserve their own empirical discipline. It finds that externally applied task pressure sharply raises the probability of collapse while naturally occurring pressure is only a modest predictor of later failure, that errors are temporally correlated rather than independent, and that locally valid actions keep running after the agent's overall task state has already gone wrong. Larger horizons permit larger error cascades, but their scale stays bounded by the task and by model capability. The work is under review and rests on a position paper's framing rather than a single benchmark.
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Two sparse-autoencoder analyses have resisted scaling: matching semantically similar features across layers, and compressing large feature circuits into interpretable supernodes. This paper argues both are the same underlying problem, estimating semantic distances between SAE features that sit on different activation manifolds. Its representation treats each feature not as a single decoder vector but as an activation-weighted distribution over the hidden states expressing it, projects those distributions into a shared reference space, and compares them with Wasserstein distance. The representation is proved invariant to activation rescaling and stable under perturbation, and recovers true matches under finite-sample margin conditions. Empirically it outperformed decoder-vector and LLM-based baselines and captured subtle functional distinctions between related features, and it compressed large feature circuits into interpretable supernodes automatically. The limitation is that this is interpretability tooling: the paper demonstrates better feature matching and circuit compression, not that downstream interpretability claims become more accurate.